Wrench with concave jaw teeth



Feb. 21, 1967 J. E. SWANSTRONLJR. ETAL 3,304,817 WRENCH WITH CONGAVE JAW TEETH Filed Feb. 2 1965 10 I INVENTORS' damv .8! mmzm k 6." Emma marrow BY A 4 M W {KW 4770mm:

United States Patent 3,304,817 WRENCH WITH CONCAVE JAW TEETH John E. Swanstrom, Jr., and Swan Elmer Swanson, Duluth Minn., assignors to Diamond Tool and Horseshoe Co., Duluth, Minn., a corporation of Minnesota Filed Feb. 26, 1965, Ser. No. 435,452 4 Claims. (Cl. 81-67) Our invention relates to wrenches and tools with toothed concave gripping surfaces and more particularly to an improved chain wrench in which a toothed gripping portion of the wrench has a concave surface.

While chain wrenches and other gripping tools are well known and in use, they previously had the disadvantage of lacking immediate positive gripping action when pressure is applied to its gripping surfaces. Further, wrenches and tools with toothed gripping surfaces have the tendency of becoming dull and ineffective in a gripping action. The improved wrench or tool of the present invention provides a gripping surface with teeth directed angularly from a central position on the gripping surface with the teeth forming a concave surface across the width of the wrench and a relatively straight line surface across the side edges of the gripping surface to provide for point type contact of the gripping surface with the object to be engaged and positive gripping action as a result thereof. Further, the wrench of the present invention provides a structure for a chain wrench in which a chain is so connected to the gripping head to fit against portions of the head in such a manner that the wrench is readily accessible to provide a working function in hard to get at places for either direction of rotation. In addition, the improved wrench provides special bearing surfaces for the chain to increase the gripping action and prevent slippage.

With the present invention, the concave gripping surface across the width of a tool overcomes the problem of tooth dullage and scraping of an object with tool slippage. The point type contact bites into the metal of the object or pipe to be worked providing a positive gripping action which insures long tool life. Further the gripping surfaces of the improved tool may be readily maintained by grinding off dull edges to substantially increase the working efficiency and life of the tool.

Therefore it is the principal object of this invention to provide an improved tool having a concave gripping surface.

It is also an object of this invention to provide an im- 1 proved chain type wrench.

Another object of this invention is to provide in a wrench of this type an arrangement which provides ease in hooking onto an object to be moved in hard to get at places with near perfect clearance for either direction of tool operation.

A further object of this invention is to provide an improved chain type wrench with a concave gripping surface to provide for point type contact with the object to be moved.

Another object of this invention is to provide an improved chain type wrench in which the contact with the pipe is a multiple point contact so as to increase gripping power and eliminate pipe shaving.

A further object of this invention is to provide an improved chain type wrench in which the toothed gripping surfaces may be sharpened by a simple grinding operation for increasing tool life.

A still further object of this invention is to provide in an improved chain type wrench a rectangular head configuration with a connection to the chain and a hook surface for the chain together with bearing surfaces for the chain in the working function which are equidistantly spaced from the center of the wrench for workage under minimum clearance conditions.

These and other objects will become apparent from a reading of the attached description together with the drawings wherein:

FIGURE 1 is a side elevation view of the improved chain wrench with a portion of the handle broken away and encircling the pipe.

FIGURE 2 is a schematic diagram of the head of the improved wrench showing a relationship of the teeth forming the gripping surface and the bearing points of the chain thereon.

FIGURE 3 is a perspective view of the wrench of FIG- URE 1 to show the gripping face of the wrench.

FIGURE 4 is a sectional view of the wrench of FIG- URE 1 taken along the lines 4-4 therein to show contact of the gripping surface with an object to be worked.

FIGURE 5 is a schematic view of the head of the wrench showing sharpening of the teeth which form the gripping surface to overcome tooth dullage.

Our improved chain type wrench is shown in plan view in FIGURE 1 as incorporating a handle 10 mounting a head member 20 angularly disposed to the extent of the handle and generally rectangular as viewed in side and end elevations. Head 20 has an inner gripping surface generally indicated at 25 having a plurality of teeth or tooth members 2-6 thereon which are angularly disposed on the inner gripping surface with respect to a centrally located recess 28 on the gripping surfaces. The head 20 has pivotally mounted at one edge of its outer surface a chain member, indicated generally '30, made up of a plurality of links 31 connected together by transversely extending pins 32 which extend beyond the width of the links and bear against the surface of the head, as will be hereinafter noted. One extremity of the chain 30 is pivotally connected to the outer edge of the head through a pivot pin 35. The opposite edge of the head at the outer surface thereof includes hook members indicated at 40 adapted to engage and hold pins 32 on the chain 30 as the chain encircles an object, such as a pipe indicated at 50 in FIGURE 1.

As will be seen in FIGURES 2 and 3, the crest of the teeth or tooth members 26 forming the gripping surface of the head extend across the face of the same in concave fashion, preferably normal to the sides of the head. The teeth may be positioned at an angle to the sides of the head, other than normal thereto, if desired. Further, the ends of the teeth at the sides form substantially a straight line, such as is indicated by the broken line 55 in FIG- URE 2, except for teeth or.to0th members 26 adjacent the recess 28 at the center of the grip ing surface and 26' near the outer extremities of the gripping surface. As will be seen in FIGURES 1 and 2, the teeth are disposed angularly away from the recess 28 and provide the gripping surface which will accommodate any size object such as a pipe within the limits of the extent of the chain. The ends of the head have notches 60 and 62 therein which notches are adapted to receive the body of the links 31 of the chain 30 with the pins 32 thereon extending beyond the width of the notches and engaging the end surfaces of the head. Thus as will be seen in FIGURE 1, the pins 32 extend the width of the head to engage the hooks and the end surfaces of the head. In addition, the ends of the gripping surface are ch-amfered or beveled, as at 61 and 63, respectively, adjacent the ends of the notches 60 and 62 to provide a bearing surface for the pins and reduce the overall wrench width such that it may be readily worked in inaccessible places. Further, the bearing surfaces insure positive gripping action on thepipe by gripping surface of the wrench and are particularly desirable in positive gripping of small dimension objects.

With this configuration, the head with respect to the hearing surfaces, the anchoring point and the hooks is generally symmetrical about the recess 28. Thus as will be seen in FIGURE 2, the spacing A between the bearing surfaces 61 and 63 with respect to the center of the recess 28 is identical and a similar relationship exists between the location of the hooks 40 and the anchor pin 35 with the chain with respect to the centrally located recess 28, as indicated by the letter B. Further, the distance between the pivot pin 35 and the edges of the teeth on the gripping surface is the same as the distance from the hooks 40 and the edges of the teeth, as indicated by the letter C.

The gripping surface 25 of the wrench is concave such as is indicated at 70 in FIGURES 3, 4 and 5, the concavity extending between the sides of the head such that as the teeth members thereon grip a pipe extending between the sides a point contact is obtained between the teeth at the outer edges of the head or sides of the head as distinguished from line type constant in which the entire surface of the tooth contacts the pipe. This permits the gripping surface to bite into the surface of the pipe for a positive grip as the wrench is operated so that it does not slip and shave the metal of the pipe dulling the head or the teeth members of the gripping surface. Generally speaking, the width or extent of the object gripped will be greater than the width of the gripping surface of the tool or wrench such that the point contact will take place along the edges of the tool, but as can readily beseen, any object having a width less than that of the tool will also bear against an adequate gripping surface.

The straight line type engaging surface, indicated at 55 in FIGURE 2, insures that this gripping action will take place for substantially any size object or pipe within the limits of the chain length. The point type contact obtained by the concave gripping surface across the inner face of the head further insures a substantially longer life for the tool inasmuch as dulling of the same is cut down and slippage of the wrench on the pipe is eliminated. However, the points or ends of the teeth do become dull through extensive usage, the side surfaces of the head may be ground down to remove the bent and dulled material and provide new edges of the extremities of the concave surface which will again provide the point type contact and positive gripping action. Thus, as will be seen in FIGURE 5, the edges may be shaved as at 80 to eliminate the dull oints.

With the improved wrench, the locationing or anchoring of the chain on the surface of the head, the fitting of the chain positively into the edges of the head and bearing on the extremities of the same substantially decreases the overall envelope of the tool making it easy to work in either direction on pipes or fittings positioned in hard to get at places. In the operation of the wrench, the chain 30 is positioned to encircle the object to be moved and the extremity of the chain drawn over the slot 60 such that the pins 32 thereon may slide into the books 40 at this extremity of the head to secure the chain around the object to be worked. When the chain is so positioned around an object, such as the pipe 50, the improved gripping surface will allow movement of the wrench in either direction of motion to turn the pipe in a conventional manner. The spacing of the bearing surfaces 61, 63, the anchoring point 35 and the hooks 40 with respect to the recess 28 in the inner face or gripping surface 25 of the head provides a balanced location enabling the tool to be used for either direction of rotation and in a manner which will insure engagement of the gripping surface for positive turning action. The gripping surface with its concavity insures point type contact at the extremities of the gripping surface which bite into the metal of the pipe or fitting to be moved preventing slippage thereon and shaving of the pipe to further provide positive turning action. Elimination of slippage increases tool life in that it prevents dulling of the gripping surface. The straight line contact of the side edges insures that this gripping surface may be applied to varying size pipes or other shaped objects. It will be understood that recess 28 and the short teeth 26 permit the wrench to be used on small dimensional objects.

In the event that tool dullage does occur at these points through usage, the tool may be reconditioned by grinding the side surfaces of the head to eliminate the dulled portion of the teeth and provide sharp tooth extremities on the side edges for point type contact with the pipes or fittings to substantially increase tool life.

In considering this invention it should be remembered that the present disclosure is illustrative only and that we Wish to be limited only by the appended claims. For example the concave surface of the teeth may be formed in pipe wrenches, pliers or other such tools without departing from the spirit of the invention.

What is claimed is:

1. A chain wrench comprising, an elongated handle having at one end an angularly offset head member, the head member having an inner toothed gripping surface with a centrally located recess, said gripping surface being made up of a plurality of teeth extending normal to the edges of the surface, each of said teeth being formed with a gripping surface defined by the crest of all the teeth being concave and of substantially equal curvature and being angularly disposed in opposite directions away from the centrally located recess in which the crests of substantially all of the teeth to either side of the recess at the edges of the head member lie in the same plane, a chain member having a plurality of pinned links, means anchoring one extremity of said chain member pivotally at one end of the outside surface of said head member, and hook means adapted to receive and hold the pins of the links positioned at the other end of the outside surface of said head member with the anchoring means and the hook means being spaced equidistantly from the recess in the gripping surface of the head member.

2. The chain wrench of claim 1 and including bearing surfaces at the ends of the inner gripping surface of the head which bearing surfaces are equidistantly spaced from the centrally located recess and with one bearing surface being spaced from the hook means the same distance that the other bearing surface is spaced from the anchoring means the ends of said head having slots formed therein such that said links fit within the slots and said pins thereon bear on said bearing surfaces.

3. A hand held gripping tool comprising, a fixed head and a cooperative moving part adapted to engage an object to be gripped to urge the same against the fixed head, handle means connected to the fixed head, the fixed head having an inner gripping surface formed by a plurality of teeth, substantially all of the tips of the teeth at the outer edges of the head being disposed in the same plane with each tooth having a gripping surface formed by the crest of all the teeth being concave and having substantially the same radius of curvature.

References Cited by the Examiner UNITED STATES PATENTS 514,721 2/1894 Mahnicke 81-68 722,144 3/ 1903 Rhinelander 8 l-68 944,468 12/ 1909 Stanley 8168 1,522,804 1/1925 Carlson 81l86 1,824,944 9/1931 Carnelli 81-70 2,795,986 6/1957 Petersen 8168 WILLIAM FELDMAN, Primary Examiner.

JAMES L. JONES, JR., Examiner. 

3. A HAND HELD GRIPPING TOOL COMPRISING, A FIXED HEAD AND A COOPERATIVE MOVING PART ADAPTED TO ENGAGE AN OBJECT TO BE GRIPPED TO URGE THE SAME AGAINST THE FIXED HEAD, HANDLE MEANS CONNECTED TO THE FIXED HEAD, THE FIXED HEAD HAVING AN INNER GRIPPING SURFACE FORMED BY A PLURALITY OF TEETH, SUBSTANTIALLY ALL OF THE TIPS OF THE TEETH AT THE OUTER EDGES OF THE HEAD BEING DISPOSED IN THE SAME PLANE WITH EACH TOOTH HAVING A GRIPPING SURFACE FORMED BY THE CREST OF ALL THE TEETH BEING CONCAVE AND HAVING SUBSTANTIALLY THE SAME RADIUS OF CURVATURE. 